Chromatography and chromatographic columns are utilized in the vast majority of analytical and biological laboratories. The literature is therefore replete with scientific articles, text books, and patents on chromatography techniques. These techniques are sometimes referred to by the functionality of the chromatographic media, for example, ion-exchange, affinity, hydrophobic interaction, etc. Other references are sometimes inferred from the process or the physical characteristics of the process used, e.g., high performance liquid chromatography (HPLC), thin layer chromatography, hollow fibers, etc.
Purification is crucial to a host of industries, including the pharmaceutical, biotechnical, chemical, and food processing. In all, the purity of the product affects it efficacy, safety, cost, and general utility. Purification media affect the overall performance of the products being purified. For organism-made (genetically-engineered) drugs, purification needs are more complex as the purification process of genetically engineered human drugs often constitutes the largest share of their manufacturing cost. Additionally, sources of raw materials vary widely, and, in general, the component to be isolated represents a very small portion of the total quantity of the raw material.
In the present invention, by separation it is meant a process where all or a large number of components are separated, e.g., in chromatographic applications. By purification, it is meant the purification of a single, or a few compounds of interest, as in pharmaceuticals applications. The present invention's main purposes are toward application as purification tools. As such, the invention is distinguished with the advantage of not addressing the numerous aliquots characteristic of chromatography. Although the present invention is particularly directed toward purification, in some cases, the terms separation and purification are used interchangeably, and distinctions will be noted where warranted. Also, particles, particulates, and beads are used interchangeably.
Generally, purification media are present in two broad classes: polymeric particles, for example gel particulates (beads); and membrane-based products such as hollow fibers and flat sheets.
Gel beads are widely used as purification media. As the beads are not self-supporting, they are commonly packed in ‘columns’ e.g., chromatography columns. High capacity gel beads are porous throughout the inside of the beads. Packed beads columns possess unfavorable flow characteristics as will be detailed below. Some chromatographic particles were suggested to address flow shortcomings, e.g., Perfusive particles which possess larger through pores (U.S. Pat. No. 5,019,270).
Commercial-scale packed columns are of considerable size, particularly height, and thus require high pressure to achieve meaningful fluid flow. This imposes significant problems for large scale preparations where the columns are required to process hundreds of gallons, as in some fermentation applications. The high pressure requirement, which can be thousands of pounds per square inch (PSI), adds technical and cost challenges, may cause loss of potency if the target molecule is delicate, as is the case with many protein drugs. The high pressure can also deform and ultimately collapse the gel beads.
Membrane-based products, e.g., hollow fibers can be fast but their lower capacity limits their purification scale.
Monolithic-type columns have gained more use in recent years to provide improvements on chromatographic columns performance e.g., less band broadening, which aid in better band separation. They are small, usually in capillary form, see for example U.S. Pat. No. 6,210,570, and commercially available columns, e.g., Chromolith® columns, obtainable from Merck Co. Monolithic columns, because of their small size and flow rates are not suitable for large scale purification. Additionally, monolithic columns contain no lumen and thus are distinguished from the embodiments in the present invention.
Because of the interest and important applications, there exist numerous patents and scientific publications concerning the various aspects of separation and purification, in fields such as chromatography, electrophoresis, filtration, etc. Numerous forms of columns, separation media beds, and membranes have been described.
U.S. Pat. No. 8,496,819 to Shimizu et al, describes modification to monolithic columns with a filler layer encircling a monolithic rod.
U.S. Pat. No. 7,261,812 to Karp, et al., describes chromatographic separation devices that include multiple batch-processed columns joined by a body structure and adapted to perform parallel analyses. The invention deals with particulate-packed columns, where liquid-permeable frits of various types may be used to retain stationary phase material within columns.
U.S. Pat. No. 7,217,359 to Nakanishi, et al. describes a column for a liquid chromatograph having a honeycomb substrate including holes through which a sample flows and a separation phase filled in the holes. The honeycomb structure apparently forms capillaries to improve separations. An example is given for the separation of nitrobenzene from toluene. No guidance was given such that the body described in the invention can be assembled to give the advantages of the parallel flow described in the present invention; as it does not contain a lumen.
U.S. Pat. No. 7,211,189, (also U.S. Pat. No. 6,780,314) to Jinno, et al. describes a separation chromatography column, which comprises a hollow capillary containing long fibers as a stationary phase, with the long fibers packed inside the hollow capillary, and act to improve the gas and liquid chromatographic separation.
U.S. Pat. No. 7,074,331 to Allington, et al. describes permeable polymeric monolithic materials prepared in a column casing. In one embodiment, the permeable polymeric monolithic materials are polymerized while pressure is applied through a piston having a smooth piston head in contact with the polymerization mixture. The pressure eliminates wall effect, shrinkage and swelling. However, the remarks regarding monolithic columns stated above are applicable.
U.S. Pat. No. 6,749,749 to Xie, et al. describes a permeable polymeric monolithic materials prepared in a column casing, with improvements on swelling and wall effects. Refer to the comments above regarding such monolithic columns.
U.S. Pat. No. 6,652,745 to Gjerde, et al., describes a separation column and method for separating a mixture of double stranded DNA fragments by Matched Ion Polynucleotide Chromatography. The method uses a cylindrical column with an ID greater than about 5 mm and contains polymer beads. This will suffer from the variable flow rates through and around the beads as described herein, which the present invention offers solutions to alleviate.
U.S. Pat. No. 5,935,429, to Liao, et al. describes chromatography columns containing a continuous solid bed spanning the cross section of the column, the bed containing flow channels. Radial flow characteristics of the present invention are absent due to lack of a lumen in U.S. Pat. No. 5,935,429.
U.S. Pat. No. 5,714,074 to Karlsson, et al. describes improvements on methods of filling a liquid chromatographic column with particulate separation medium. The remarks on the disadvantages of packed particulates columns are to be considered.
U.S. Pat. No. 5,453,185 (also U.S. Pat. No. 5,334,310) to Frechet, et al. describes a process similar to monolithic columns, where the column containing a separation medium in the form of a macro porous polymer plug is disclosed. The column contains at least one macro porous polymer plug, prepared using a polymerization process described therein.
U.S. Pat. No. 5,200,150 (also U.S. Pat. No. 5,061,355) to Rose, Jr describe a method of preparing a microcapillary gel separation column for electrophoresis comprises using photo initiator and forming a polymer plug by illuminating an initiation section of the tube.
U.S. Pat. No. 4,986,909 (also U.S. Pat. No. 4,743,373 and U.S. Pat. No. 4,675,104) to Rai, et al. describes chromatography column with a stationary phase that comprises a plurality of layers of swellable fibrous matrix in sheet form and having a spacer means between each layer for permitting controlled swelling, with means for distributing the sample through the stationary phase chamber segments.
U.S. Pat. No. 4,865,729 (and to a similar configuration in U.S. Pat. No. 4,676,898) to Saxena, et al., describes improvement on thin layer chromatography, having a horizontal flow of the liquid through the separating medium utilizing a fluid distribution system, the latter including a screen or mesh arrangement, and where the separation medium constitutes a thin layer, plate or wafer-like separation medium. The sample components are adsorbed onto the separation medium through the capillary action.
U.S. Pat. No. 4,604,198 to Dailey et al., discloses a multi-cartridge chromatography housing and fluid distribution, with a plurality of cartridge holders and an inlet fluid manifold means for distributing the fluid.
U.S. Pat. No. 4,512,897 to Crowder, III, et al. describes a separation column with a porous matrix of fiber having particulate immobilized therein, wherein at least one of the fiber or particulate is effective for molecular separation.
U.S. Pat. No. 4,496,461 to Leeke, et al., describes a chromatography column that comprises a swellable fibrous matrix in sheet form. The sheet is spirally wound around the longitudinal axis to form a plurality of layers around the axis.
U.S. Pat. No. 3,948,775 to Otani, et al., describes a horizontal multiple-chamber, packed column structure for adsorptive separation process wherein loading and unloading of packing material is facilitated, the packing material is described as particulate.
My U.S. Pat. No. 6,562,573 describes materials and methods usable for the purification of polyelectrolytes, such as nucleic acids and proteins, with separation media that possess pH-dependent groups with pKa value in the range of about 5 to about 7. Separation of the nucleic acids or proteins from a separation medium is effected at a neutral or higher pH.